Various types of electrical switching circuits are disclosed in the prior art which are controlled by a single push button spring-biased switch which releases when pressure is removed from the switch. For example, U.S. Pat. No. 4,538,074 describes a switching circuit which includes a first transistor for providing power of an electronic instrument, and a second transistor connected to the first transistor for controlling the first transistor. A push button switch is provided which serves to turn the circuit on or off as the switch is successively momentarily pressed and released. U.S. Pat. No. 4,112,764 discloses an automatic switching circuit which is responsive to the momentary operation of a push button switch to turn "on", and which remains "on" for a predetermined time interval after the switch has been pressed and released.
The switching circuit of the present invention is also capable of turning its controlled instrumentality "on" or "off" by means of a single spring-biased push button switch. However, the switching circuit of the invention has an additional feature in that it has a dual function to provide a latched control of the instrumentality when the switch is pressed momentarily and released; or to turn "on" the instrumentality only so long as the switch is operated when the switch is pressed for a longer interval.
Specifically, the switching circuit of the invention in the embodiment to be described includes a manually operated push button spring-biased switch which, when momentarily closed and released, causes the switching circuit to turn "on" and to remain "on" until the push button switch is again momentarily operated; and the switching circuit of the invention has an additional feature in that when the push button switch is pressed for a longer time interval, the switching circuit will remain "on" only so long as the switch is pressed, and will turn "off" when the switch is released.
A feature of the switching circuit of the invention is that it may be incorporated into a single integrated circuit chip.